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Girls who are obese at 11 years old show lower academic achievement at ages 11, 13, and 16 compared with those of a healthy weight, even after factoring out a number of possible influences. Photo courtesy of Shutterstock.

Preadolescence, commonly referred to as the "tween" years, is a developmental period marked by rapid physical and emotional change. A new study found that girls who are obese at age 11 had lower academic achievement at ages 11, 13, and 16 when compared with healthy weight tweens, even after factoring out a number of possible influences, including IQ. The most comprehensive study to date of the relationship between obesity and educational achievement during preadolescence was led by Dr. Josephine N. Booth, School of Psychology at the University of Dundee, who noted, "There is a clear pattern which shows that girls who are in the obese range are performing more poorly than their counterparts in the healthy weight range throughout their teenage years."

The Tween Years

How do we grow from children into adults? The progression of human maturity is commonly considered to pass through different phases: early and late childhood, pre-adolescence, puberty, adolescence, and early adulthood. Each of these periods is tied to a general age range, with children moving through each phase in an individual manner. Yet, of all the developmental periods, early adolescence or the tween years are often seen as involving some of the most profound changes on many different levels. In particular, this is the period when children begin to face the biological transformations of puberty and the psychological shifts that accompany their emerging sexuality.

Researchers from the Sandy Spring Friends School have outlined typical characteristics of preadolescents whose bodies are undergoing more rapid changes than any other period in their lives, excluding infancy. Among these common traits is a feeling of extreme self-consciousness, swift emotional swings, an intensity of feeling, and a greater tendency to give into impulses (when compared to an adult). Some tweens may appear self-assured even if they are actually experiencing a loss of self-confidence. At the same time, most tweens have begun to reason. Meanwhile, home and school are exerting the greatest influence on most tweens during this period of their lives and so many researchers believe the interplay among all these factors may be long-term. Such reasoning guided the current study.

Long-term Effects of Obesity during Preadolescence

To conduct the current study, a team of researchers examined data from the Avon Longitudinal Study of Parents and Children, a long-term health research project. The team measured not only participants' height and weight but also academic achievement as assessed by national tests for nearly 6,000 children. At 11 years old, 71.4 percent of the total participants were classed as healthy weight (1,935 male; 2,325 female), 13.3 percent were classed as overweight (372 male; 420 female) and 15.3 percent were classed as obese (448 male; 466 female). The researchers tracked these preadolescents over the next five years, measuring weight and test grades during that time.

The results of the study offer more than a few surprises. For females, being obese at 11 predicted lower test scores by one third of a grade at age 16 even after the researchers factored out a number of possible influences, including IQ, symptoms of depression, socio-economic level, mother’s educational level, and the age at which the girls began menstruation. This achievement difference, when translated into actual school grades, would mean a grade D instead of a grade C, the researchers stated. Yet the same was not true among the males, who showed no consistent relationship between obesity at age 11 and test abilities.

Additionally, the researchers came upon another unusual finding after examining data for participants whose weight status changed over the period of the study. (For example, a participant considered overweight at 11 may have lost weight and so was re-categorized as healthy weight at age 16.) The team grouped the participants based on changes in their weight status: 67.7 percent were categorized as stable healthy weight; 15.8 percent were stable overweight/obese; 4.8 percent became overweight from healthy weight; 1.2 percent became obese from healthy weight; 2.2 percent became obese from overweight; and 8.3 percent became healthy weight from being overweight/obese.

When the researchers re-examined the data based on weight status changes, they found that being overweight or obese at age 16 was not as detrimental to test results if participants had been a healthy weight at age 11. Being overweight in the tween years had greater impact and significance, apparently, than being overweight at any other age.

“This study suggests that obesity in adolescence is associated with poorer subsequent academic attainment for females, and that the magnitude of the relationship may be considered important,” wrote the authors in their study published in the International Journal of Obesity. “Moreover, the present study suggests that the relationship between obesity and subsequent academic attainment is likely to be causal.”

Dr. John Reilly, University of Strathclyde and principal investigator of the study, suggested that further work is needed to understand why obesity may negatively influence academic achievement. “But it is clear that teenagers, parents, and policymakers in education and public health should be aware of the lifelong educational and economic impact of obesity," he noted.